Abstract: A method for system documentation includes photographing at least part of a system from at least two directions to obtain photographs with a camera having a film plane and a measuring grid plate in front of the film plane. The photographs are digitized. Center lines for individual system parts are separately determined. The digitized photographs are evaluated and a three-dimensional image of the system is prepared with a CAD method from the course of the center lines, for a three-dimensional representation of the system. An apparatus for system documentation includes a camera having a film plane and a measuring grid plate in front of the film plane for taking a photograph of at least part of a system. A digitizing apparatus is provided for the photograph. An apparatus for determining a center line of the system part is connected downstream of the digitizing apparatus. A CAD system is connected downstream of the apparatus for determining the center line.